The objective is to develop a highly optimized SPECT system for 3-D brain and torso organ imaging with dynamic capability. The specific aim is to design, develop, and test a Triangular SPECT Scanner based on three rectangular NaI(Tl) gamma cameras of 16"x9" FOV for High Sensitivity SPECT. Sensitivity improvement would be 450% for brain by matched fan beam collimation, and 300% for body organs, over the current single-head systems, reducing the current 30 min. imaging time down to 7-10 min. Another major aim is to develop 3-D mapping capability of rCBF by continuous CW and CCW rotation for full projection data collection in each 120 degrees, with time resolution down to 5 seconds. Note that this camera-based system allows collimator design flexibility for resolution-sensitivity trade-off. For the brain, three detectors make a tight triangle with 10" diam. FOV imaging volume. For torso organs, the three detectors follow the body contour orbit for best resolution. For fast dynamic imaging, three detectors rotate continuously CW and CCW with the reversing time greater than 1 second. Technological innovation is the drastic reduction of SPECT imaging time, particularly important in very sick patients and pediatric imaging. This system also allows efficient 3-D dynamic imaging of physiological processes, matching with the current active brain agents search. Because of its versatility to accommodate both traditional imaging procedures as well as new fast dynamic imaging, this system will evolve into a major clinical work horse.